Heat-resistant crimped yarn

ABSTRACT

The invention provides heat-resistant crimped yarn, of which the constituent heat-resistant high-functional fibers are prevented as much as possible from being deteriorated under heat in the process of producing the yarn. Not losing excellent properties of heat resistance and flame retardancy intrinsic to the heat-resistant high-functional fibers, the crimped yarn has a good elongation percentage in stretch, a good stretch modulus of elasticity and a good appearance, and it fluffs little and releases little dust. The heat-resistant crimped yarn comprises heat-resistant high-functional fibers, and is characterized in that it does not deteriorate under heat, and that its elongation percentage in stretch is at least 6%, its stretch modulus of elasticity is at least 40%, and its tenacity falls between 0.15 and 3.5 N/tex.

This application is a 371 of PCT/JP00/09006 filed Dec. 19, 2000.

TECHNICAL FIELD

The present invention relates to heat-resistant crimped yarn comprisingheat-resistant high-functional fibers such as aramid fibers, and to amethod for producing it. More precisely, the invention relates toheat-resistant crimped yarn which has not only excellent heatresistance, flame retardancy and high tenacity characteristics, but alsoa good elongation percentage in stretch, a good stretch modulus ofelasticity and a good appearance, and which fluffs little and releaseslittle dust; and relates to a method for producing the heat-resistantcrimped yarn characterized by treatment with high-temperaturehigh-pressure steam or high-temperature high-pressure water or by dryheat treatment.

The invention also relates to a bulky and stretchable fibrous product ofthe heat-resistant crimped yarn. In particular, it relates to workingclothes and gloves necessary for protecting workers' bodies and hands invarious workplaces, for example, those for steel workers working aroundhigh-temperature blast furnaces, those for sheet metal welders, thosefor farmers, those for painters in the field of automobiles or electricand electronic appliances, those for workers in the field of precisionmachines, airplanes or information systems, those for sportsmen, thosefor surgeons, etc.

BACKGROUND ART

General thermoplastic synthetic fibers such as nylon or polyester fibersmelt at about 250° C. or so. However, heat-resistant high-functionalfibers such as aramid fibers, holaromatic polyester fibers andpolyparaphenylene-benzobisoxazole fibers do not melt at about 250° C. orso, and their decomposition temperature is about 500° C. or so and ishigh. The critical oxygen index of the non-heat-resistant generalfibers, nylon or polyester fibers is about 20 or so, and the fibers wellburn in air. However, the critical oxygen index of the heat-resistanthigh-functional fibers such as those mentioned above is at least about25, and the fibers may burn in air when they are brought near to a heatsource of flames, but could not continue to burn if they are moved awayfrom the flames. To that effect, the heat-resistant high-functionalfibers have excellent heat resistance and flame retardancy. Therefore,aramid fibers, a type of heat-resistant high-functional fibers arefavorable to clothes for use in high risk of exposure to flames and hightemperatures, for example, for fireman's clothes, racer's clothes,steelworker's clothes, welder's clothes, etc. Above all, para-aramidfibers having the advantages of heat resistance and high tenacity aremuch used for sportsman's clothes, working clothes, ropes, tire cordsand others that are required to have high tear strength and heatresistance. In addition, as they are hardly cut with edged tools, thefibers are also used for working gloves. On the other hand, meta-aramidfibers are resistant to heat and have good weather resistance andchemical resistance, and they are used for fireman's clothes,heat-insulating filters, heat-resistant dust-collecting filters,electric insulators, etc.

Heretofore, when the heat-resistant high-functional fibers are formedinto fibrous products such as clothes, they are used merely in the formof non-crimped filaments or spun yarn. However, even when suchnon-crimped yarn of filaments or spun yarn is worked into fabrics andformed into clothes such as fireman's clothes, racer's clothes andworking clothes, the resulting clothes are poorly elastic as the yarnitself is not elastic. As a result, when the clothes are worn, they areproblematic in that their feel is not good and they are unsuitable toexercises and working activities.

In particular, working gloves made of conventional non-crimped yarn areunsuitable to use in the industrial fields of airplanes, informationsystems and precision machines in which precision parts are handled, asthey do not well fit with worker's hands. Using the gloves in thoseindustrial fields often results in the reduction in the workingefficiency. In the field of medicine, for example, in the field ofsurgical operations of treating AIDS cases and the like that will causeinfection by blood, the surgeons wear rubber gloves or elastomer gloves(hereinafter referred to as rubber gloves) to protect themselves fromthe patient's blood. Ambulance men take care of unspecified, wounded orsick persons, and they wear rubber gloves to protect themselves from theblood and body fluid of patients who are not yet identified asinfectious. However, rubber gloves will be readily broken by operationtools such as surgical knives, and they could not completely protect themedical and surgical workers such as physicians, surgeons and ambulancemen, from surgical knives, syringe needles and others stained withpatient's blood. In that situation, it may be taken into considerationto wear woven or knitted gloves of heat-resistant high-functional fiberswith high mechanical strength such as those mentioned above, insiderubber gloves. However, as mentioned hereinabove, the conventionalgloves of heat-resistant high-functional fibers are poorly elastic andtherefore lower the working efficiency of the medical and surgicalworkers such as physicians, surgeons and ambulance men. Accordingly,thin, elastic and tough gloves capable of being worn inside rubbergloves without detracting from the working efficiency are desired.

Heretofore, however, spun yarn is produced by spinning short fibersgenerally having a length of around 38 mm or around 51 mm or so, and theedges of the short fibers often protrude out of the surface of the spunyarn to form fluffs therearound. Working clothes and gloves made of spunyarn of heat-resistant high-functional fibers release the fluffs, whenrubbed while they are used. Therefore, using them in clean rooms with nodust in air therein, or in painting factories in which dust, whenadhered to the surfaces of painted products, detracts from thecommercial value of the products is problematic. In that situation,working clothes, gloves and other fibrous products of heat-resistanthigh-functional fibers, which fluff little and release little dust aredesired.

As described hereinabove, fibrous products of non-crimped yarn ofheat-resistant high-functional fibers are unsuitable to exercises andworking activities, and they fluff and release dust. In order to solvethe problems, it is desired to provide heat-resistant crimped which hasa good elongation percentage in stretch, a good stretch modulus ofelasticity and a good appearance, not losing the excellentcharacteristics of good heat resistance and flame retardancy intrinsicto heat-resistant high-functional fibers, and which fluffs little andreleases little dust.

To meet the requirements now in the market, various studies andproposals have been made, relating to heat-resistant crimped yarn and toa method for crimping heat-resistant high-functional fibers (JapanesePatent Laid-Open Nos. 19818/1973, 114923/1978, 27117/1991). Concretely,one proposal is to apply a method for crimping ordinary thermoplasticsynthetic fibers such as nylon or polyester fibers. For example, knownis a method of forcedly crimping high-elasticity fibers such aspara-aramid fibers mixed with low-elasticity fibers (Japanese PatentLaid-Open No. 192839/1989). Also known is crimped yarn produced by afalse-twisting method in which aramid fibers are false-twisted andcrimped by the use of a non-contact heater heated at a temperature notlower than that at which the fibers begin to decompose but lower thanthe decomposition point of the fibers (for meta-aramid fibers, thetemperature is 390° C. or higher but lower than 460° C.), and thereaftersubjected to thermal relaxation (Japanese Patent Laid-Open No.280120/1994).

However, the known methods could not still solve all the outstandingtechnical problems which are how to produce high-quality crimped yarnhaving a good elongation percentage in stretch and a good stretchmodulus of elasticity; how to prevent yarn quality deterioration, forexample, tenacity reduction and color change under heat of yarnproduced, and how to prevent the yarn from fluffing and from being cutor broken; and how to realize easy process control, simplification ofproduction lines, increased productivity, and cost reduction. Atpresent, therefore, no one has succeeded in industrial production ofheat-resistant crimped yarn having a good elongation percentage instretch and so on, not losing the physical properties intrinsic to theconstituent fibers.

DISCLOSURE OF THE INVENTION

In view of the problems in the related art noted above, one object ofthe present invention is to provide heat-resistant crimped yarn whichcomprises heat-resistant high-functional fibers and has a goodelongation percentage in stretch, a good stretch modulus of elasticityand a good appearance, for which the quality deterioration of theconstituent heat-resistant high-functional fibers through heat treatmentin the production process is reduced as much as possible, and whichtherefore does not lose the excellent properties of good heat resistanceand flame retardancy intrinsic to the heat-resistant high-functionalfibers, and which fluffs little and releases little dust.

Another object of the invention is to provide a method for producing theheat-resistant crimped yarn practicable in point of the productivity,the necessary equipment and the production costs.

Still another object of the invention is to provide fibrous products,especially gloves of which the advantages are that (a) they are elasticand resistant to heat, and they have good mechanical strength and a goodappearance, (b) they well fit wearer's bodies including hands and aresuitable to exercises and working activities, (c) they fluff little andrelease little dust, and (d) they are easy to produce on an industrialscale as the process control is easy, the productivity is high and theproduction costs is low.

We, the present inventors have assiduously studied so as to attain theobjects as above, and, as a result, have found that, when heat-resistanthigh-functional fibers are used in the form of crimped yarn having aspecific elongation percentage in stretch, a specific stretch modulus ofelasticity and a specific tenacity and not deteriorating under heat, inproducing fibrous products, then the suitability of the resultingfibrous products to exercises and working activities is significantlyimproved, as compared with those used in the form of non-crimped yarnsuch as filaments or spun yarn, and that the fibrous products flufflittle and release little dust even when rubbed while they are used. Thefibrous products, which we have produced in the manner as above, solveall the outstanding problems in the prior art mentioned hereinabove.

We have further studied the method for producing the heat-resistantcrimped yarn, and, as a result, have found that, when heat-resistanthigh-functional fiber filaments are first twisted in a primary twistingstep, then heat-set for twist fixation through treatment withhigh-temperature high-pressure steam or high-temperature high-pressurewater or through dry heat treatment, and finally untwisted by againtwisting them in the direction opposite to the primary twistingdirection, then the above-mentioned heat-resistant crimped yarn of highquality can be produced.

Heat-resistant high-functional fiber filaments are slippery. Thereforeweaving or knitting them into gloves by the use of weaving or knittingmachines is often difficult. In this connection, we have found that theheat-resistant crimped yarn of the invention solves the problem. We havefurther found that bulky and stretchable fibrous products such as glovesmade of the heat-resistant crimped yarn of the invention have anadvantage in that they fluff little and release little fluff. As somentioned hereinabove, spun yarn of short fibers fluffs since the edgesof the constituent short fibers protrude out of the surface of the yarn,and therefore, fibrous products made of spun yarn of heat-resistanthigh-functional fibers release fluffs when rubbed while they are used.As opposed to such spun yarn, the heat-resistant crimped yarn of theinvention is composed of long fibers and therefore has no fluffs on itssurface. Not having edges of short fibers therearound, therefore,fibrous products such as working clothes made of the heat-resistantcrimped yarn of the invention fluff little and therefore do not releasefluffs even when rubbed while they are used.

In the industrial fields of precision machines, airplanes andinformation systems, for example, in the working site for fabricatingelectronic parts for airplanes, computers and the like, the workingspace must be kept all the time clean. If the working gloves used in thesite are deteriorated, they will soon release fibrous dust in theworking space, in which, however, the trouble is unacceptable.Accordingly, the fibrous products especially the gloves of the inventionare especially useful in these industrial fields, as having theadvantage of fluffing little and releasing little dust. In paintingfactories in which construction materials of aluminum, electric andelectronic appliances for household use, or automobile parts arepainted, fibrous fluffs and dust, if they have been adhered to thesurfaces of the painted products, detract from the commercial value ofthe products. In these, therefore, the fibrous products especially thegloves of the invention are also useful, since they fluff little andrelease little dust.

Having further studied, we, the present inventors have completed thepresent invention.

Specifically, the invention relates to the following:

(1) Heat-resistant crimped yarn not deteriorating under heat, whichcomprises heat-resistant high-functional fibers having a mono-filamentfineness of from 0.02 to 1 tex, and of which the elongation percentagein stretch is at least 6%, the stretch modulus of elasticity is at least40%, and the tenacity falls between 0.15 and 3.5 N/tex;

(2) The heat-resistant crimped yarn of above (1), wherein theheat-resistant high-functional fibers are para-aramid fibers,holaromatic polyester fibers or polyparaphenylene-benzobisoxazolefibers, and of which the tenacity falls between 0.5 and 3.5 N/tex;

(3) The heat-resistant crimped yarn of above (2), for which thepara-aramid fibers are polyparaphenylene-terephthalamide fibers;

(4) The heat-resistant crimped yarn of above (1), wherein theheat-resistant high-functional fibers are meta-aramid fibers, and ofwhich the elongation percentage in stretch falls between 50 and 300%;

(5) The heat-resistant crimped yarn of above (4), wherein themeta-aramid fibers are polymetaphenylene-isophthalamide fibers;

(6) A bulky and stretchable fibrous product of the heat-resistantcrimped yarn of any of above (1) to (5), wherein the amount of theheat-resistant crimped yarn is for at least 50% of the fibrous part ofthe product;

(7) The bulky and stretchable fibrous product of above (6), which is forgloves;

(8) The gloves of above (7) for use in the industrial fields ofprecision machines, airplanes, information systems, automobiles,electric and electronic appliances, and in the field of surgicaloperations and sanitary facilities;

(9) The bulky and stretchable fibrous product of above (6), which is forfireman's clothes, racer's clothes, steel worker's clothes, welder'sclothes or painter's clothes;

(10) A method for producing heat-resistant crimped yarn, which comprisestwisting heat-resistant high-functional fiber filaments, heat-settingthem through treatment with high-temperature high-pressure steam orhigh-temperature high-pressure water, and thereafter untwisting them;

(11) The method for producing heat-resistant crimped yarn of above (10),wherein the heat-resistant high-functional fiber filaments are twistedto a twist parameter, K represented by the following formula, of from5,000 to 11,000, and are heat-set through treatment withhigh-temperature high-pressure steam or high-temperature high-pressurewater at a temperature falling between 130 and 250° C.:

K=t×D ^(1/2)

wherein t indicates the count of twists (/m) of the filaments; and Dindicates the fineness (tex) thereof;

(12) The method for producing heat-resistant crimped yarn of above (10)or (11), wherein the heat-resistant high-functional fibers are selectedfrom the group consisting of para-aramid fibers, meta-aramid fibers,holaromatic polyester fibers and polyparaphenylene-benzobisoxazolefibers;

(13) The method for producing heat-resistant crimped yarn of above (12),wherein the para-aramid fibers are polyparaphenylene-terephthalamidefibers;

(14) The method for producing heat-resistant crimped yarn of any ofabove (10) to (13), wherein the heat-resistant crimped yarn produced hasan elongation percentage in stretch of at least 6% and a stretch modulusof elasticity of at least 40%;

(15) A bulky and stretchable fibrous product made of the heat-resistantcrimped yarn obtained in the production method of above (12);

(16) A method for producing heat-resistant crimped yarn, which comprisestwisting heat-resistant high-functional fiber filaments, heat-settingthem through dry heat treatment at a temperature not higher than thedecomposition point of the heat-resistant high-functional fibers, andthereafter untwisting them;

(17) The method for producing heat-resistant crimped yarn of above (16),wherein the heat-resistant high-functional fiber filaments are twistedto a twist parameter, K represented by the following formula, of from5,000 to 11,000, then heat-set through dry heat treatment at atemperature falling between 140 and 390° C., and thereafter untwisted:

K=t×D ^(1/2)

wherein t indicates the count of twists (/m) of the filaments; and Dindicates the fineness (tex) thereof;

(18) The method for producing heat-resistant crimped yarn of above (16)or (17), wherein the process of twisting the heat-resistanthigh-functional fiber filaments, heat-setting them through dry heattreatment and thereafter untwisting them is effected continuously;

(19) The method for producing heat-resistant crimped yarn of any ofabove (16) to (18), wherein the dry heat treatment is effected at atemperature falling between 200 and 300° C.;

(20) The method for producing heat-resistant crimped yarn of any one ofabove (16) to (19), wherein the heat-resistant high-functional fibersare selected from the group consisting of para-aramid fibers,meta-aramid fibers, holaromatic polyester fibers andpolyparaphenylene-benzobisoxazole fibers;

(21) The method for producing heat-resistant crimped yarn of any one ofabove (16) to (20), wherein the para-aramid fibers arepolyparaphenylene-terephthalamide fibers;

(22) The method for producing heat-resistant crimped yarn of any one ofabove (16) to (21), wherein the heat-resistant crimped yarn produced hasan elongation percentage in stretch of at least 6% and a stretch modulusof elasticity of at least 40%;

(23) A bulky and stretchable fibrous product made of the heat-resistantcrimped yarn obtained in the method of any one of above (16) to (22);

(24) A method for producing heat-resistant crimped yarn, which comprisesknitting heat-resistant high-functional fiber filaments into a knittedfabric, then heat-setting the knitted fabric through dry heat treatmentor through treatment with high-temperature high-pressure steam orhigh-temperature high-pressure water, and thereafter unknitting it;

(25) The method for producing heat-resistant crimped yarn of above (24),wherein the knitted fabric of heat-resistant high-functional fiberfilaments is heat-set through treatment with high-temperaturehigh-pressure steam or high-temperature high-pressure water at atemperature falling between 130 and 250° C. for a period of time fallingbetween 2 and 100 minutes, and then this is unknitted;

(26) The method for producing heat-resistant crimped yarn of above (24),wherein the knitted fabric of heat-resistant high-functional fiberfilaments is heat-set through with dry heat treatment at a temperaturefalling between 140 and 390° C., and then this is unknitted;

(27) The method for producing heat-resistant crimped yarn of above (25)or (26), wherein the heat-resistant crimped yarn produced has theelongation percentage in stretch of at least 6.5%;

(28) Gloves made by weaving or knitting yarn that contains crimped yarnof heat-resistant high-functional fibers;

(29) Gloves of above (28), wherein the crimped yarn has an elongationpercentage in stretch of from 6% to 30% and a stretch modulus ofelasticity of from 40 to 100%;

(30) Gloves of above (28) or (29), wherein the heat-resistanthigh-functional fibers are selected from the group consisting ofpara-aramid fibers, meta-aramid fibers, holaromatic polyester fibers andpolyparaphenylene-benzobisoxazole fibers;

(31) Gloves of above (30), wherein the para-aramid fibers arepolyparaphenylene-terephthalamide fibers;

(32) Gloves of any of above (28) to (31), wherein the crimped yarn ofheat-resistant high-functional fibers is produced by twistingheat-resistant high-functional fiber filaments, heat-setting themthrough dry heat treatment or through treatment with high-temperaturehigh-pressure steam or high-temperature high-pressure water, andthereafter untwisting them; and

(33) Gloves of any of above (28) to (32), which are for use in theindustrial fields of precision machines, airplanes, information systems,or in the field of surgical operations and sanitary facilities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the relationship between the twist parameter of fiberfilaments not treated with saturated steam, and the elongationpercentage in stretch, one typical parameter, of crimped yarn.

FIG. 2 shows the relationship between the processing time and theelongation percentage in stretch of crimped yarn.

FIG. 3 shows the relationship between the processing temperature and theelongation percentage in stretch of crimped yarn.

FIG. 4 shows the relationship between the temperature in dry heattreatment and the tensile strength of crimped yarn.

FIG. 5 shows the relationship between the temperature in dry heattreatment and the lightness of crimped yarn.

BEST MODES OF CARRYING OUT THE INVENTION

The invention provides heat-resistant crimped yarn not deterioratingunder heat, which comprises heat-resistant high-functional fibers havinga monofilament fineness of from 0.02 to 1 tex, and of which theelongation percentage in stretch is at least about 6%, the stretchmodulus of elasticity is at least about 40%, and the tenacity fallsbetween about 0.15 and 3.5 N/tex or so.

Preferably, the heat-resistant high-functional fibers for use in theinvention have a critical oxygen index of at least about 25 and athermal decomposition point measured in differential scanningcalorimetry of not lower than about 400° C. The critical oxygen indexindicates the flame retardancy of the fibers; and the thermaldecomposition point indicates the heat resistance of the fibers.Examples of the fibers are aramid fibers, holaromatic fibers (e.g.,Kuraray's Vectran®), polyparaphenylene-benzoxazole fibers (e.g.,Toyobo's Zylon®), polybenzimidazole fibers, polyamidimide fibers (e.g.,Rhone-poulenc industries's Kermel®), polyimide fibers, etc. Aramidfibers include meta-aramid fibers and para-aramid fibers. Examples ofmeta-aramid fibers are meta-holaromatic polyamide fibers such aspolymetaphenylene-isophthalamide fibers (e.g., DuPont's Nomex®), etc.Examples of para-aramid fibers are para-holaromatic polyamide fiberssuch as polyparaphenylene-terephthalamide fibers (e.g., Toray-DuPont'sCommercial product named Kevlar®),copolyparaphenylene-3,4′-diphenylether-terephthalamide fibers (e.g.,Teijin's Commercial product named Technora®), etc.

The heat-resistant crimped yarn of the invention may be composed of onetype of heat-resistant high-functional fibers such as those mentionedabove, or may comprise two or more different types of suchheat-resistant high-functional fibers. It may be in the form ofconjugated yarn, combined or twisted with any other known fibers such aspolyester, nylon, polyvinyl alcohol fibers, etc.

The monofilament fineness of the heat-resistant high-functional fibersto be used in the invention falls between about 0.02 and 1 tex or so,but preferably between about 0.05 and 0.6 tex or so, more preferablybetween about 0.08 and 0.5 tex or so, for the flexibility of theheat-resistant crimped yarn of the invention and for easy production ofthe yarn.

The total fineness of the heat-resistant high-functional fiber filamentsto be used in the invention is not specifically defined so far as thethickness of the filaments is enough for their process ability intotwisted yarn and knitted fabrics. In view of the step of twisting thefilaments into twisted yarn and the step of knitting them into knittedfabrics in the process of producing the heat-resistant crimped yarn ofthe invention, however, the total fineness of the fiber filamentspreferably falls between about 5 and 5000 tex or so.

The fineness referred to herein is indicated by a unit of tex, as sostipulated in JIS L 0101 (1999). For example, 1 tex means that a fiberfilament having a length of 1000 m has a weight of 1 g; and 10 tex meansthat a fiber filament having a length of 1000 m has a weight of 10 g.Fiber filaments having a larger value of tex are thicker.

One preferred embodiment of the heat-resistant crimped yarn of theinvention, which comprises heat-resistant high-functional fibersselected from para-aramid fibers, holaromatic polyester fibers orpolyparaphenylene-benzobisoxazole fibers, has an elongation percentagein stretch of at least about 6% or so, more preferably from about 10 to50% or so, even more preferably from about 15 to 40% or so, a stretchmodulus of elasticity of at least about 40% or so, more preferably fromabout 50 to 100% or so, even more preferably from about 60 to 100% orso, and a tenacity of from about 0.15 to 3.5 N/tex or so, morepreferably from about 0.5 to 3.5 N/tex or so.

Another preferred embodiment of the heat-resistant crimped yarn of theinvention, in which the heat-resistant high-functional fibers aremeta-aramid fibers, has an elongation percentage in stretch of at leastabout 6% or so, more preferably at least about 50% or so, even morepreferably from about 50 to 300% or so, still more preferably from about70 to 300% or so, a stretch modulus of elasticity of at least about 40%or so, more preferably from about 50 to 100% or so, even more preferablyfrom about 70 to 100% or so, and a tenacity of from about 0.15 to 1.0N/tex or so.

The heat-resistant crimped yarn of the invention is characterized inthat it does not substantially deteriorate under heat. Qualitydeterioration under heat means that the physical properties of theheat-resistant crimped yarn are lowered and the appearance thereof isworsened while or after the yarn is processed under heat. Moreconcretely, for example, the tenacity of the yarn is lowered, the colorthereof is changed, and the yarn fluffs or is cut or broken as a resultof the heat treatment. One criterion indicating the absence of thetenacity reduction is that the tenacity retention of the yarn after heattreatment is at least 30%, preferably at least 40%, more preferably atleast 50%. The tenacity retention is represented by the followingformula:

Tenacity Retention (%)={tenacity of heat-resistant crimped yarn(N/tex)/tenacity of heat-resistant high-functional fiber filaments notprocessed under heat (N/tex)}×100.

The color change of the yarn after heat treatment depends on the type ofthe heat-resistant high-functional fibers that constitute the yarn, andindiscriminately discussing it shall be evaded herein. For example, onecriterion indicating the absence of color change of the yarn thatcomprises meta-aramid fibers may be that the lightness of the yarn afterheat treatment is at least about 80% or so, preferably at least 85% orso of the lightness of the yarn before heat treatment.

The invention provides a bulky and stretchable fibrous product made ofthe heat-resistant crimped yarn. The fibrous product may be made of theheat-resistant crimped yarn only, or may be a mixed-woven ormixed-knitted product of the yarn with any other type of yarn ofdifferent fibers. For the mixed-woven or mixed-knitted product, however,it is desirable that the heat-resistant crimped yarn of the inventionaccounts for at least about 5% or so, more preferably at lest about 25%or so, even more preferably at least about 50% or so of the fibrouscomponent of the product. Other types of yarn except the heat-resistantcrimped yarn that may be in the product are not specifically defined,and may be any known ones.

The fibrous product of the invention is not specifically defined,including, for example, fabrics made by weaving or knitting yarn whichcontains the heat-resistant crimped yarn; clothes made of the fabrics,for example, gloves such as heat-resistant safety gloves, fireman'sclothes, racer's clothes, steel worker's clothes, welder's clothes,painter's clothes and the like for use in high risk of exposure toflames and high-temperature heat; heat-resistant materials forindustrial use such as heat-resistant dust-collecting filters, etc.;ropes, tire cords, etc.

The fibrous product can be produced with ease in any per-se knownmethod. For example, for producing gloves, favorably used arecommercially-available computer glove knitting machines, SFG and STJ(from Shima Precision Machinery).

The fibrous product may be used either singly or as combined with anyother heat-resistant or flame-retardant products. If desired, thefibrous product may be processed in any per-se known manner. Forexample, the gloves of the invention may be directly used in variousworking activities, or, as the case may be, a part of each glove,especially the outer surface of the palm thereof or the entire outersurface thereof may be coated with resin. The resin for the purposeincludes, for example, polyvinyl chloride resin, latex, polyurethaneresin, natural rubber, synthetic rubber, etc. Coated with such resin,the mechanical strength of the gloves increases and the gloves are notslippery in holding objects. Coating the gloves with resin may beeffected in any per-se known manner. Over the gloves of the invention,one may wear any other rubber gloves or elastomer gloves.

The invention further provides a method for producing heat-resistantcrimped yarn practicable in point of the productivity, the necessaryequipment and the production costs.

The method comprises twisting heat-resistant high-functional fiberfilaments such as aramid fiber filaments, heat-setting them throughtreatment with high-temperature high-pressure steam or high-temperaturehigh-pressure water (this is hereinafter referred to as high-temperaturehigh pressure steam treatment) or through dry heat treatment, andthereafter untwisting them. The heat-resistant high-functional fiberfilaments may be spun yarn or filament yarn prepared in any per-se knownmanner. Especially preferred is filament yarn, as fluffing little andreleasing little dust.

More concretely, in general, heat-resistant high-functional fiberfilaments are first twisted (this is the primary twisting step in whichthe filaments are twisted in the direction of S or Z); then optionallywound up around a heat-resistant bobbin of aluminum or the like; andheat-set for twist fixation at a temperature falling within apredetermined range. Next, these are untwisted by again twisting them inthe direction opposite to the primary twisting (that is, in thedirection of Z or S) to give the intended, heat-resistant crimped yarn.

In the method of the invention, each monofilament of the startingfilaments is, after twisted in the primary twisting step, deformed tohave complicated spiral morphology, and its morphology is fixed as it isthrough the heat treatment that follows the twisting step. Then, in thenext untwisting step, the twisted monofilaments are released from thetwisting force restraint but they still retain the primary-twistedmorphology owing to their shape memory effect. As a result, themonofilaments individually act to restore their twisted situation basedon their memory, and finally they are in the form of crimped yarn.

As so mentioned hereinabove, the method for producing the heat-resistantcrimped yarn of the invention includes two different means forheat-setting, high-temperature high-pressure steam treatment and dryheat treatment.

The process of high-temperature high-pressure steam treatment has anadvantage that the fiber filaments can be heated uniformly.Specifically, in the process, there is almost no probability that thefiber filaments are partly too much heated and are thereforedeteriorated or, contrary to this, heating them is partly not enough andtherefore they could not be fully heat-set.

On the other hand, the advantage of dry heat treatment is that (a) itdoes not require high-temperature high-pressure steam orhigh-temperature high-pressure water for treatment (hereinafter referredto as high-temperature high-pressure steam), and therefore the fiberfilaments can be twisted and heat-set under atmospheric pressure, notrequiring autoclaves, and (b) not only batch process but also continuousprocess of, for example, passing the fiber filaments in ahigh-temperature zone applies to it, and therefore, hot air as well as afluidized bed may apply to the high-temperature zone.

The method of treatment with high-temperature high-pressure steam isdescribed in detail hereinunder.

In the method, heat-resistant high-functional fiber filaments are firsttwisted in a primary twisting step. The filaments may be in any form offilament yarn or spun yarn. Preferred is filament yarn, as fluffinglittle and releasing little dust.

In the primary twisting step, preferably, the fiber filaments aretwisted to a twist parameter, K represented by a formula, K=t×D^(1/2)(wherein t indicates the count of twists (/m) of the filaments, andindicates the fineness (tex) thereof), of from about 5,000 to 11,000 orso, more preferably from about 6,000 to 9,000 or so. The filaments aredesired to be twisted to such a suitable degree that the yarn to befinally obtained is appropriately crimped, but if they are too muchtwisted, the fibers constituting them will be cut and damaged. To evadethe problem, it is desirable that the twist parameter of the fiberfilaments to be twisted falls within the defined range.

The twist parameter, K, is an index of indicating the degree of twistingof the fiber filaments, not depending on the thickness of the filaments.The larger the value of the twist parameter is, the higher the twistdegree is.

In the primary twisting step, usable is any per-se known twistingmachine, including, for example, a ring twister, a double twister, anItaly twister, etc.

Preferably, the twisted yarn is wound up around a bobbin. However, incase where the filaments are wound up around a bobbin while they aretwisted, it is unnecessary to rewind them. The bobbin referred to hereinis usually an ordinary cylindrical winding core around which yarn iswound up. Any per-se known bobbin is usable herein. For example,preferred are heat-resistant bobbins of aluminum or the like. Alsopreferably, the heat-resistant bobbin for use herein is worked to havesmall through-holes in its entire surface in order that high-temperaturehigh-pressure steam can easily pass through it in the next heat-settingstep.

Preferably, the thickness of the filament cheese or the filament coneformed by winding up the twisted yarn around the bobbin is at leastabout 15 mm; and the winding density thereof falls between about 0.4 and1.0 g/cm³ or so, more preferably between about 0.5 and 0.9 g/cm³or so,even more preferably between about 0.6 and 0.9 g/cm³ or so.

Next, the thus-twisted yarn is exposed to high-temperature high-pressuresteam at a temperature falling within a specifically defined range.Through this high-temperature high-pressure steam treatment, the twistedyarn is heat-set.

The high-temperature high-pressure steam treatment may be effected inany per-se known manner. For example, the twisted yarn is processed inan autoclave with high-temperature high-pressure steam being introducedthereinto. For the treatment, any per-se known autoclave may be used.One example of the structure of the autoclave for use herein is equippedwith a steam duct through which high-temperature high-pressure steam isfed thereinto; a water drainage valve; an exhaust valve via which theautoclave is degassed after treatment; an inlet mouth through which thebobbin with the twisted yarn being wound therearound in the previousstep is led into it; and a lid capable of being opened and shut tohermetically seal it.

The temperature for the high-temperature high-pressure steam treatmentmay fall between about 130 and 250° C. or so, but preferably betweenabout 130 and 220° C. or so, more preferably between about 140 and 200°C. or so, even more preferably between about 150 and 200° C. or so. Thetemperature range is preferred, as ensuring practicable crimped yarn notdeteriorating the constituent fibers.

The pressure for the treatment is described. In case where thehigh-temperature high-pressure steam for the treatment is saturatedsteam, its pressure shall be physicochemically defined by itstemperature. Concretely, the pressure of saturated steam at thelowermost temperature 130° C. is 2.70×10⁵ Pa, and is 38.97×10⁵ Pa at theuppermost temperature 250° C. Therefore, in the invention, thehigh-temperature high-pressure steam treatment is preferably effected ata temperature falling between about 130° C. and 250° C. or so and undera pressure falling between about 2.70×10⁵ Pa and 39.0×10⁵ Pa or so.However, the steam for the treatment in the invention is not limited tosaturated steam only, and its pressure may fall between about 2.7×10⁵ Paand 39.0×10⁵ Pa or so. Needless-to-say, the steam pressure could not beabove the saturated steam pressure at the same temperature. Especiallypreferably, the high-temperature high-pressure steam treatment iseffected at a temperature falling between about 130° C. and 220° C. orso and under a pressure falling between about 2.7×10⁵ Pa and 23.2×10⁵ Paor so, more preferably at a temperature falling between about 140° C.and 220° C. or so and under a pressure falling between about 3.5×10⁵ Paand 23.2×10⁵ Pa or so, even more preferably at a temperature fallingbetween about 150° C. and 200° C. or so and under a pressure fallingbetween about 4.8×10⁵ Pa and 15.6×10⁵ Pa or so.

In place of such high-temperature high-pressure steam, high-temperaturehigh-pressure water can also be used herein. In this case, the watertemperature may fall between about 130 and 250° C. or so, but preferablybetween about 130 and 220° C., more preferably between about 140 and220° C. or so, even more preferably between about 150 and 200° C. or so;and the water pressure may fall between about 2.70×10⁵ Pa and 39.0×10⁵Pa or so, more preferably between about 2.7×10⁵ Pa and 23.2×10⁵ Pa orso, even more preferably between about 3.5×10⁵ Pa and 23.2×10⁵ Pa or so,still more preferably between about 4.8×10⁵ Pa and 15.6×10⁵ Pa or so.For the high-temperature high-pressure water treatment, the expressions“high-temperature high-pressure steam” and “steam” given hereinabove andhereinunder shall be replaced by “high-temperature high-pressure water”and “water”, respectively.

The time for the high-temperature high-pressure steam treatment is notindiscriminately defined, as varying depending on the amount of thefilaments wound around a bobbin to be exposed to high-temperaturehigh-pressure steam. It is enough that the filaments are kept at thepredetermined temperature for a few minutes. Preferably, however, thetime for the treatment falls between about 2 and 100 minutes or so, morepreferably between about 3 and 60 minutes or so. The defined range ofthe time for the treatment is preferred for more uniformly heat-settingboth the surface and the inside of the filaments wound around a bobbin,not deteriorating the constituent fibers. After having been thus treatedwith such high-temperature high-pressure steam, the filaments woundaround a bobbin may be forcedly cooled by applying cold air thereto, butare preferably cooled in room-temperature air.

After treated with high-temperature high-pressure steam, the twistedyarn is untwisted by again twisting it in the direction opposite to theprimary twisting, and the heat-resistant crimped yarn of the inventionis thus produced. In the untwisting step, also used is any per-se knowntwisting machine, like in the primary twisting step.

Next described is the method of dry heat treatment.

For dry heat treatment, any mode of batch operation or false-twistingoperation can be used, in which neither high-temperature high-pressuresteam nor high-temperature high-pressure water is used for heat-setting.Namely, heat treatment with neither high-temperature high-pressure steamnor high-temperature high-pressure water is referred to as dry heattreatment.

In any mode of batch operation or false-twisting operation, the dry heattreatment may be optionally followed by thermal relaxation. Concretely,for example, the crimped yarn is thermally relaxed, while it isstretched in some degree. The advantage of such thermal relaxation isthat the torque of the crimped yarn can be reduced, not detracting fromthe bulkiness of the yarn.

The batch process of dry heat treatment is described.

In the method, heat-resistant high-functional fiber filaments are firsttwisted in the primary twisting step. The filaments may be in any offilament yarn or spun yarn. However, preferred is filament yarn, sinceit fluffs little and releases little dust as mentioned hereinabove. Inthe primary twisting step, preferably, the fiber filaments are twistedto a twist parameter, K of from about 5,000 to 11,000 or so, morepreferably from about 6,000 to 9,000 or so. The filaments are desired tobe twisted to such a suitable degree that the yarn to be finallyobtained is appropriately crimped, but if they are too much twisted, thefibers constituting them will be cut and damaged. To evade the problem,it is desirable that the twist parameter of the fiber filaments to betwisted falls within the defined range.

In the primary twisting step, usable is any per-se known twistingmachine, including, for example, a ring twister, a double twister, anItaly twister, etc.

Preferably, the twisted yarn is wound up around a bobbin. However, incase where the filaments are wound up around a bobbin while they aretwisted, it is unnecessary to rewind them. Any per-se known bobbin isusable herein. For example, preferred are heat-resistant bobbins ofaluminum or the like.

Next, the thus-twisted yarn is heat-set through dry heat treatment at atemperature falling within a specifically defined range.

The temperature for the heat treatment shall be lower than thedecomposition point of the constituent fibers. Preferably, it fallsbetween about 140 and 390° C. or so, more preferably between about 170and 350° C. or so, most preferably between about 200 and 330° C. or so.Through the heat treatment within the preferred temperature range, theyarn is crimped to a level suitable to practical use, and is notdeteriorated. The dry heat treatment of the invention does not requirehigh temperatures over the decomposition point of the constituentfibers. Through the treatment, therefore, the yarn is not substantiallydeteriorated. For example, the tenacity of the yarn is not lowered; thecolor thereof does not change; and the yarn does not fluff, and is notcut or damaged. Concretely, one criterion indicating the absence of thetenacity reduction is that the tenacity retention of the yarn after heattreatment is at least 30%, preferably at least 40%, more preferably atleast 50%. The tenacity retention is represented by the numericalformula mentioned above. The color change of the yarn after heattreatment depends on the type of the heat-resistant high-functionalfibers that constitute the yarn, and indiscriminately discussing itshall be evaded herein. For example, in the case of meta-aramid fibers,one criterion indicating the absence of color change of the yarn may bethat the lightness of the yarn after heat treatment is at least about80% or so, preferably at least 85% or so of the lightness of the yarnbefore heat treatment.

The heater for heat treatment maybe any of contact heaters ornon-contact heaters. Heating the yarn may be effected in any per-seknown manner with hot air or by the use of a fluidized-bed heatingsystem.

The heating time for batch operation shall not be indiscriminatelydiscussed, as varying depending on the type of the constituent fibers,the thickness of the filaments and the heating temperature. In general,however, it preferably falls between about 2 and 100 minutes or so, morepreferably between about 10 and 100 minutes or so, even more preferablybetween 20 and 40 minutes or so. The defined range of the time for thetreatment is preferred for more uniformly heat-setting both the surfaceand the inside of the filaments wound around a bobbin, not deterioratingthe constituent fibers.

The dry heat treatment may be affected under increased pressure, reducedpressure or atmospheric pressure. Preferably, it is affected underatmospheric pressure.

After having been thus heat-set through dry heat treatment, the twistedyarn is untwisted by again twisting it in the direction opposite to theprimary twisting direction, and the heat-resistant crimped yarn of theinvention is thus produced. After treating with heat, the yarn may beforcedly cooled with cold air, but is preferably left cooled inroom-temperature air. In the untwisting step, also used is any per-seknown twisting machine, like in the primary twisting step.

Next described is the false-twisting method.

In the false-twisting method, the yarn unwound from the filament cheese(this is wound around a cylindrical winding core, bobbin) via a let-offroller is rewound up around a winding bobbin, after having been ledthereto via a take-up roll. Between the let-off roll and the take-uproll, disposed is a false-twisting spindle. The yarn running in themanner is nipped by the false-twisting spindle, while being wound aroundthe pin of the spindle, and the spindle is rotated in that condition,whereby the yarn running between the let-off roll and the false-twistingspindle is twisted in the direction S. With that, the thus-twisted yarnis heat-set, and then this is again twisted in the opposite direction,for example in the direction Z, between the false-twisting device andthe take-up roller, whereby the yarn is untwisted to be crimped yarn.The space between the false-twisting device and the take-up roll is acooling zone, in which the yarn is preferably left cooled with air. Inplace of using the false-twisting spindle in the manner as above, theyarn may be false-twisted in a different manner. For example, the yarnis brought into contact with the inner wall of a cylinder rotating athigh speed or with the outer periphery of a disc also rotating at highspeed, or with the surface of a belt running at high speed, whereby theyarn is false-twisted owing to the friction against the rotating orrunning medium.

In the false-twisting method, the heat-resistant high-functional fiberfilaments may be either filament yarn or spun yarn. However, preferredis filament yarn, as fluffing little.

When the yarn is twisted by the use of a false-twisting spindle, itstwist parameter K preferably falls between about 5,000 and 11,000 or so,more preferably between about 6,000 and 9,000 or so. This is in orderthat the yarn can be crimped to a desired degree and the constituentfibers are prevented from being cut or damaged.

In this method, the yarn may be twisted in any desired manner, forexample, using a spindle, a nip belt, etc., and the twisting mode is notspecifically defined. In the method of twisting the yarn with a spindle,usable is a single-pin spinner. In the invention, however, preferred aremulti-pin spinners, for example, four-pin spinners. In case where yarnis twisted with a single-pin spinner that is generally used in thespindle-twisting method, heat-resistant high-functional fiber filamentsmust be wound once around the pin. In that case, however, the yarn ofheat-resistant high-functional fiber filaments may be cut or damagedwhile being twisted, since the filaments are easily cut by friction.Contrary to this, in case where a multi-pin spinner, especially afour-pin spinner in which two upper pins and two lower pins arealternately aligned is used, and when the yarn to be twisted is passedin zigzags through the space between the neighboring pins so that theyarn can enter the spindle through the upper center part thereof and cango out through the lower center part thereof, then the yarn can betwisted more efficiently. In that case, the yarn is folded between theneighboring pins and is therefore twisted by frictional resistancetherebetween.

The temperature for the heat-setting treatment in the false-twistingmethod is the same as that in the batch method mentioned hereinabove.However, the heat treatment effect in the false-twisting method ishigher than that in the batch method. Therefore, the heating time in thefalse-twisting method may fall between about 0.5 and 300 seconds or so,preferably between about 1 and 120 seconds or so, though depending onthe thickness of the yarn to be processed therein.

Like in the batch method, the heater for heat treatment in thefalse-twisting method may be any of contact heaters or non-contactheaters. Heating the yarn may be effected in any per-se known mannerwith hot air or by the use of a fluidized-bed heating system. Even whena contact heater is used in the false-twisting method, tar-like mistdeposits little in the heating line. Therefore, even yarn of aramidfibers, which often release tar-like mist deposits, can be stablyprocessed according to the false-twisting method, not requiringfrequently cleaning the surface of the line on which the yarn beingprocessed runs.

Like in the batch method, the dry heat treatment in the false-twistingmethod may be affected under increased pressure, reduced pressure oratmospheric pressure. Preferably, it is affected under atmosphericpressure.

The heat-resistant crimped yarn of the invention can be produced in anyother method such as that mentioned below, not limited to the productionmethods mentioned hereinabove. For example, heat-resistanthigh-functional fiber filaments are knitted into a knitted fabric, thenthe knitted fabric is heat-set, and thereafter unknitted intoheat-resistant crimped yarn. For heat-setting the knitted fabric in themethod, the fabric may be subjected to the above-mentionedhigh-temperature high-pressure steam treatment or dry heat treatment.The details of the condition for the treatment may be the same as thosementioned hereinabove. In this method, preferred is high-temperaturehigh-pressure steam treatment.

When the knitted fabric is prepared in the method, the degree oftwisting the filaments is preferably lower, as the fabric restrains theconstituent filaments. For example, it is desirable that the twistparameter of the filaments falls between 0 and 500, more preferablynearer to 0.

The invention is described concretely with reference to the followingExamples.

The physical properties of the samples produced are measured andevaluated according to the methods mentioned below.

Critical Oxygen Index:

Measured according to JIS K7201 (1999) that indicates a combustion testfor polymer materials based on the critical oxygen index of testedsamples.

Thermal Decomposition Point:

Measured according to JIS K7120 (1987) that indicates a method formeasuring the thermal weight loss of plastics.

Elasticity:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to the Test Method8.11.A, the elongation percentage in stretch and the stretch modulus ofelasticity of each sample are determined.

Fineness:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to the Test Method8.3, the fineness based on the corrected weight of each sample isdetermined.

Tensile Strength:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to the Test Method8.5.1, the tensile strength of each sample is determined. In order toprevent the monofilaments in each sample tested from being disorderedand to ensure uniform stress to all the constituent mono-filaments, thesample is twisted to a twist parameter, K of 1000, before tested.

Snarl Index:

Measured according to JIS L1095 (1999) that indicates a method fortesting ordinary spun yarn. According to the Test Method 9.17.2.B, thesnarl index of each sample is determined.

EXAMPLE 1

Used was polyparaphenylene-terephthalamide fiber filament yarn(Toray-DuPont's Commercial product named Kevlar®) having a criticaloxygen index of 29, a thermal decomposition point of 537° C., a tensilestrength of 2.03 N/tex, and a tensile modulus of 49.9 N/tex. This iscomposed of 1000 monofilaments each having a fineness of 0.167 tex, andits fineness is 167 tex. The yarn was first twisted to a twist parameterK of 6308 by the use of a ring twister (Kakigi Seisakusho's conjugatedyarn twister, Model KCT), and then heat-set with saturated steam at 180°C. for 30 minutes. Next, using the same twister, the yarn was againtwisted in the direction opposite to the primary twisting direction to atwist parameter 0, whereby this was untwisted to be crimped yarn of theinvention. The physical properties of the crimped yarn were measured.

EXAMPLES 2, 3, AND COMPARATIVE EXAMPLES 1, 2

The same yarn as in Example 1 was twisted, heat-set with saturated steamor through dry heat treatment, and untwisted in the same manner as inExample 1, except that the twist parameter in the primary twisting stepwas varied as in Table 1. The physical properties of the crimped yarnobtained herein were measured.

In Examples 2 and 3, the twist parameter falls within the preferredrange for the invention, while that in Comparative Examples 1 and 2 islower than the preferred range.

EXAMPLE 4

The same yarn as in Example 1 was used herein, except that its finenessis 22.2 tex. The yarn was twisted to a twist parameter K of 5277 in theprimary twisting step, then heat-set with saturated steam at 180° C.,and then untwisted to be crimped yarn of the invention. The physicalproperties of the crimped yarn were measured.

The data of the samples in Examples 1 to 4 and Comparative Examples 1and 2 are shown in Table 1. The relationship between the twist parameterof the yarn not heat-set with saturated steam and the elongationpercentage in stretch, one typical characteristic of the crimped yarn isshown in FIG. 1. From the data in Table 1 and FIG. 1, it is understoodthat the elongation percentage in stretch of the yarn obtained inExamples 1 to 4 is enough for practical use, but that of the yarnobtained in Comparative Examples 1 and 2 is not. This is because thetwist parameter of the yarn before heat treatment in the ComparativeExamples is low.

TABLE 1 Fineness Saturated Steam Elongation Stretch Fineness beforeCount of Twist Treatment Percentage Modulus of of Crimped treatmentTwists Parameter Temperature in Stretch Elasticity Yarn Tenacity (tex)(/m) (K) (° C.) Time (min) (%) (%) (tex) (N/tex) Example 1 167 488 6306180 30 6.6 78.0 170.0 1.14 Example 2 167 639 8258 180 30 11.9  84.5175.6 0.96 Example 3 167 763 9860 180 30 25.2  50.7 173.3 0.93 Example 422.2 1120  5277 180 30 6.5 88.8  23.1 1.21 Comp. Ex. 1 167 260 3360 18030 2.3 57.8 167.8 1.67 Comp. Ex. 2 167 375 4846 180 30 5.2 71.4 170.01.2 

EXAMPLES 5 TO 7, AND COMPARATIVE EXAMPLE 3

Heat-resistant crimped yarn of the invention was obtained in the samemanner as in Example 1, except that the twist parameter K in the primarytwisting step was 8258 and the time for saturated steam treatment fellbetween 7.5 and 60 minutes as in Table 2.

In Comparative Example 3, the same yarn as in Examples 5 to 7 wastwisted to the same degree without being subjected to saturated steamtreatment as therein, then left at room temperature for 1 day andthereafter untwisted. The physical properties of the yarn of thisComparative Example 1 were also measured. The data are all given inTable 2. The relationship between the processing time and the elongationpercentage in stretch of the crimped yarn is shown in FIG. 2. From thedata of Examples 5 to 7, Example 2 and Comparative Example 3, it isunderstood that the elongation percentage in stretch of the crimped yarndoes not vary so much even when the processing time is longer than 7.5minutes. This means that the heating time may be short to obtain theheat-resistant crimped yarn of the invention.

TABLE 2 Fineness Saturated Steam Elongation Stretch Fineness beforeCount of Twist Treatment Percentage Modulus of of Crimped treatmentTwists Parameter Temperature in Stretch Elasticity Yarn Tenacity (tex)(/m) (K) (° C.) Time (min) (%) (%) (tex) (N/tex) Example 5 167 639 8258180 7.5 16.0 72.1 170.0 0.88 Example 6 167 639 8258 180 15 12.9 79.0174.4 0.89 Example 7 167 639 8258 180 60 15.8 61.9 170.0 0.74 Example 2167 639 8258 180 30 11.9 84.5 175.6 0.96 Comp. Ex. 3 167 639 8258 nottreated  4.2 52.1 174.4 1.05

EXAMPLES 8 TO 10, AND COMPARATIVE EXAMPLES 3, 4

Heat-resistant crimped yarn of the invention was obtained in the samemanner as in Example 1, except that the twist parameter K in the primarytwisting step was 8258 and the temperature of the steam for heat-settingtreatment fell between 130 and 200° C. as in Table 3.

In Comparative Example 4, crimped yarn was obtained in the same manneras above except that the temperature of the steam for heat-settingtreatment was 120° C. The data are given in Table 3 along with those inExample 2 and Comparative Example 3. The relationship between theprocessing temperature and the elongation percentage in stretch of thecrimped yarn is shown in FIG. 3. From these, it Is understood that thetemperature of saturated steam for heat-setting treatment is preferablynot lower than 130° C. for producing practicable crimped yarn.

TABLE 3 Fineness Saturated Steam Elongation Stretch Fineness beforeCount of Twist Treatment Percentage Modulus of of Crimped treatmentTwists Parameter Temperature in Stretch Elasticity Yarn Tenacity (tex)(/m) (K) (° C.) Time (min) (%) (%) (tex) (N/tex) Example 9 167 639 8258160 30 9.9 65.2 171.1 0.67 Example 10 167 639 8258 200 30 17.1  62.8170.0 0.72 Example 2 167 639 8258 180 30 11.9  84.5 175.6 0.96 Example 8167 639 8258 130 30 6.1 81.3 175.5 1.04 Comp. Ex. 4 167 639 8258 120 304.9 55.6 173.4 0.98 Comp. Ex. 3 167 639 8258 not treated 4.2 52.1 174.41.05

EXAMPLES 11 TO 14, AND COMPARATIVE EXAMPLES 5, 6

The same yarn as in Example 1 was twisted to a twist parameter as inTable 4 by the use of a ring twister, and the twisted yarn was put intoa hot air drier and subjected dry heat treatment under the conditionshown in Table 4. Next, using the same twister, the yarn was againtwisted in the direction opposite to the primary twisting direction to atwist parameter 0, whereby this was untwisted to be heat-resistantcrimped yarn of the invention.

In Comparative Example 5, the yarn was processed in the same manner asin Example 11 except that the temperature for the dry heat treatment was130° C.

In Comparative Example 6, the yarn was processed in the same manner asin Example 12 except that the twist parameter K was 4846.

The data are given in Table 4. The relationship between the processingtemperature and the elongation percentage in stretch of the crimped yarnis shown in FIG. 3. Within the range tested, the elongation percentagein stretch of the crimped yarn that had been processed at highertemperatures either through treatment with high-temperaturehigh-pressure steam or through dry heat treatment is higher. Under thecondition herein, the elongation percentage in stretch of the crimpedyarn processed through high-temperature high-pressure steam treatment ishigher than that of the crimped yarn processed through dry heattreatment.

In Comparative Example 5, the elongation percentage in stretch of thecrimped yarn obtained is relatively low, since the temperature for thedry heat treatment for the yarn was 130° C. and was low. Accordingly, itis understood that the temperature for the dry heat treatment ispreferably not lower than 140° C. In Comparative Example 6, theelongation percentage in stretch of the crimped yarn obtained is alsorelatively low, since the count of twists in the primary twisting stepis small. Accordingly, it is understood that the twist parameter in theprimary twisting step is preferably at least 5,000.

TABLE 4 Fineness Elongation Stretch Fineness before Count of Twist DryHeat Treatment Percentage Modulus of of Crimped treatment TwistsParameter Temperature in Stretch Elasticity Yarn Tenacity (tex) (/m) (K)(° C.) Time (min) (%) (%) (tex) (N/tex) Example 11 167 639 8258 200 306.9 79.0 171.1 0.96 Example 12 167 639 8258 250 30 12.2  81.6 167.8 0.96Example 13 167 763 9860 250 30 15.4  45   173.3 0.93 Example 14 167 6398258 250 7.5 12.8  72.1 170.0 0.88 Comp. Ex. 5 167 639 8258 130 30 5.079.8 168.9 0.99 Comp. Ex. 6 167 375 4846 250 30 4.4 76.2 170.0 1.2 

EXAMPLE 15

The same filament yarn as in Example 1 except that its fineness is 22.2tex was twisted to a count of twists of 1850/m (this corresponds to atwist parameter K of 8775) by the use of an Italy twister, and 500 g ofthe thus-twisted yarn was wound up around a flanged aluminum bobbin. Inthe same manner, prepared were two filament cheeses that had beentwisted in opposite directions S, Z respectively, to the same count oftwists. These were put into an autoclave for saturated steam treatment,and exposed to saturated steam at 180° C. for 30 minutes. After cooled,the yarn was again twisted in the opposite to the primary twistingdirection to a twist parameter of 0. Thus untwisted, heat-resistantcrimped yarn of the invention was obtained.

The elongation percentage in stretch of the crimped yarn was 17.1%. Thecrimped yarn had some residual torque. To cancel their residual torque,the crimped yarns differing in the torque direction of S or Z wereparalleled to each other. The paralleled yarn has a total fineness of 88tex. This was fed into a seamless glove knitting machine, ShimaPrecision Machinery's SFG-10G Model, and knitted into working gloves ofthe invention. The cut protection performance of the thus-knitted gloveswas measured according to ASTM F1790-97, and was 6.8 N.

On the other hand, paralleled yarn was prepared by paralleling six,commercially-available woolly polyester filament yarns each having afineness of 16.5 tex (the yarn is from Toray, and this is composed of 48mono-filaments), for comparison to the heat-resistant crimped yarn ofthe invention produced in the above. The paralleled yarn had a totalfineness of 99 tex. This was knitted into gloves in the same manner asabove, and the cut protection performance of the gloves was measuredalso in the same manner as above, and was 3.5 N. From the data, it isunderstood that the cut protection performance of the gloves of theinvention is better than that of the comparative gloves.

As being made of the crimped yarn, the working gloves of the inventionproduced herein fluffs little when compared with those made of spunyarn, Kevlar®. In addition, since they are thin and highly elastic,workers wearing them can handle fine machine parts with ease.Accordingly, the gloves are favorable to, for example, workers who weldelectronic parts or who fabricate them in clean rooms, as well as topainters who paint aluminum construction materials, parts of electricand electronic appliances for household use, automobile parts, etc., forensuring safety work in such production liens and for protecting suchworkers and painters from being burned and injured by edged tools orparts.

EXAMPLE 16

500 g of the same yarn having been twisted under the same condition asin Example 15 was wound up around an aluminum bobbin, and processed inhigh-temperature high-pressure water at 180° C. for 10 minutes. Then,this was cooled, desiccated and dried. Next, this was again twisted inthe direction opposite to the primary twisting direction, to a twistparameter 0 by the use of an Italy twister, like in Example 15. Thusuntwisted, heat-resistant crimped yarn of the invention was obtained.Its elongation percentage in stretch was 18%. As being uniformlyheat-set, the crimped yarn was uniform as a whole.

EXAMPLE 17

500 g of the same yarn having been twisted under the same condition asin Example 15 was wound up around an aluminum bobbin, and exposed to hotair at 250° C. with a hot air drier for 30 minutes. After left cooled inair, this was again twisted in the direction opposite to the primarytwisting direction, to a twist parameter 0 by the use of an Italytwister, like in Example 15. Thus untwisted, heat-resistant crimped yarnof the invention was obtained. Its elongation percentage in stretch was12%. In this process, however, the heat transmission into the insidearea of the yarn layer wound around the bobbin was not enough, and theyarn could not be uniformly heat-set. As a result, the elongationpercentage in stretch of the part of the yarn not uniformly heat-set waslow, and the yarn was not crimped uniformly. This is not practicable.

However, the problem was solved by reducing the thickness of the yarnlayer wound around the bobbin to a half. In that manner, if the yarnlayer wound around the bobbin is too thick, the yarn could not beuniformly heat-set in dry heat treatment and the yarn could not becrimped uniformly. Therefore, when the crimped yarn of the invention isproduced through dry heat treatment, it is desirable that the yarn layerwound around a bobbin is not too thick.

EXAMPLE 18

This Example is to demonstrate continuous production of heat-resistantcrimped yarn of the invention in a false-twisting process. Concretely, afalse-twisting unit is disposed in a space between a heating zone havinga length of 10 m and an air-cooling zone having a length of 5 m. Yarn istwisted to a count of twists of 1760/m (this corresponds to a twistparameter K of 8258), and introduced into the zone. First, this isheat-set in the heating zone, and then untwisted in the air-coolingzone. The starting yarn is Kevlar® 22 tex of para-aramid fibers. This isthe same as the yarn processed in Example 1 except that its fineness is22 tex. The heating zone was heated at 300° C., and the feed speed ofthe yarn was 10 m/min. Regarding its physical properties, theheat-resistant crimped yarn produced herein had an elongation percentagein stretch of 12.5%, a stretch modulus of elasticity of 82.6%, afineness of 22.9 tex, and a tenacity of 0.96 N/tex.

EXAMPLE 19

The crimped yarn of para-aramid fibers Kevlar® obtained in Example 18had some residual torque. To cancel their residual torque, the crimpedyarns differing in the torque direction of S or Z were paralleled toeach other to obtain paralleled yarn. This was fed into a ShimaPrecision Machinery's 13-gauge seamless glove knitting machine, andknitted into thin gloves. Being different from gloves made of spun yarn,these gloves have the following advantages:

1) They are elastic and well fit worker's hands, and they do notinterfere with the movement of worker's hands. Wearing them, workers cando their work with ease.

2) They fluff little, and are therefore favorable to work in clean roomswhere no dust is allowed.

EXAMPLE 20

The same filament yarn of polyparaphenylene-terephthalamide fibers(Toray-DuPont's Commercial product named Kevlar®) as in Example 1 wastwisted to a count of twists of 640/m (this corresponds to a twistparameter of 8270) by the use of a ring twister, then wound up around analuminum bobbin, and heat-set through treatment with high-temperaturehigh-pressure steam, and thereafter untwisted to a twist parameter of 0by the use of the ring twister to be heat-resistant crimped yarn of theinvention. The temperature in the high-temperature high-pressure steamtreatment was 200° C., and the processing time was 15 minutes.

EXAMPLES 21 TO 24

Heat-resistant crimped yarn of the invention was produced in the samemanner as in Example 20. In place of thepolyparaphenylene-terephthalamide fibers used in Example 20, however, ahigh-elasticity type of polyparaphenylene-terephthalamide fibers(Toray-DuPont's Commercial product named Kevlar® 49) were used inExample 21; co-paraphenylene-3,4′-oxydiphenylene-terephthalamide fibers(Teijin's Commercial product named Technora®) were in Example 22;holaromatic polyester fibers (Kuraray's Commercial product namedVectran®) were in Example 23; and polybenzobisoxazole fibers (Toyobo'sCommercial product named Zylon®) were in Example 24. As in Table 5, thetwist parameter of the twisted yarn in these Examples differs from thatin Example 20.

EXAMPLE 25

Heat-resistant crimped yarn of the invention was produced in the samemanner as in Example 20. In this, however, filament yarn having asmaller fineness, 22.2 tex than that in Example 20 was used, and thenumber of twists per the unit length of the yarn was increased to 1600/m(see Table 5). Accordingly, in this, the yarn was twisted and untwistedby the use of a double twister (this is favorable to twisting yarn to alarger count of twists), being different from that in Example 20 where aring twister was used.

EXAMPLE 26

Heat-resistant crimped yarn of the invention was produced in the samemanner as in Example 25. In this, however, yarn ofpolymetaphenylene-isophthalamide fibers (DuPont's Commercial productnamed Nomex®) having a fineness of 22.2 tex was used in place of thepolyparaphenylene-terephthalamide fibers used in Example 25.

The physical properties of the heat-resistant crimped yarn obtained inExamples 20 to 26 are shown in Table 5. In Table 5, the tensilestrength, the tensile modulus, the thermal decomposition point, thecritical oxygen index, and the fineness of the starting yarn are all thephysical data of the filament yarn not processed into crimped yarn.

From the test data shown in Table 5, it is understood that theelongation percentage in stretch (this indicates the crimp degree) ofall the crimped yarns produced in Examples 20 to 26 from different fiberfilaments is 8.5% or more. In particular, the crimped yarn ofpara-aramid fibers, polyparaphenylene-terephthalamide fibers andco-polyparaphenylene-3,4′-oxydiphenylene-terephthalamide fibers, that ofmeta-aramid fibers, polymetaphenylene-isophthalamide fibers, and that ofholaromatic polyester fibers had a high elongation percentage instretch. Above all, the elongation percentage in stretch of the crimpedyarn of meta-aramid fibers, polymetaphenylene-isophthalamide fibers was104.6%, and it is comparable to the elongation percentage in stretch ofordinary crimped yarn of polyester fibers.

TABLE 5 Example 21 Chemical poly- Example 22 Example 24 Example 25Example 26 Name (trade Example 20 paraphenylene- copoly- poly- poly-poly-meta- name is in poly- terephthalamide paraphenylene-3,4′- Example23 paraphenylene- paraphenylene- phenylene- the lower paraphenylene-(high- oxydiphenylene- holaromatic benzobi- tere- isophthala- column)terephthalamide elasticity type) terepthalamide polyester soxazolephthalamide mide Physical Kevlar ® Kevlar ® 49 Technora ® Vectran ®Zylon ® Kevlar ® Nomex ® Properties (unit) Tensile (N/tex) 2.03 1.962.47 2.56 3.53 2.03 0.47 Strength Tensile (N/tex) 49.9 75 52 59 176.549.9 12.4 Modulus Thermal (° C.) 537 537 500 400 650 537 500 Decomposition Point Critical 29 29 25 28 56 29 29 Oxygen Index Fineness of (tex)167 158 167 167 111 22.2 22.2 Starting Yarn Count of (t/m) 640 640 660660 780 1600 1600 Twists Twist 8270 8045 8529 8529 8218 7539 7539Parameter Elongation (%) 28.2 29.7 27.7 22.5 8.5 32.7 104.6 Percentagein stretch Stretch (%) 64.7 46.8 40.1 45.8 56.1 75 97.5 Modulus ofElasticity Tenacity of (N/tex) 1.40 1.33 1.66 1.71 2.47 1.42 0.33Crimped Yarn

EXAMPLE 27

One 22.2 tex filament yarn of polyparaphenylene-terephthalamide fibers(Toray-DuPont's Commercial product named Kevlar®) was fed into acircular knitting machine with 150 knitting needles in total aligned ina circle having a diameter of 91 mm, and knitted into a cylindricalfabric of sheeting (plain stitch fabric). The knitted fabric was exposedto saturated steam at 200° C. for 15 minutes. Next, this was left cooledin air, and then unknitted from its last end. Thus unknitted, this gavecrimped yarn with its knitted morphology in memory. The elongationpercentage in stretch of the crimped yarn was 35%; and the stretchmodulus of elasticity thereof was 56%.

EXAMPLE 28

In the same manner as in Example 27, filament yarn ofpolymetaphenylene-isophthalamide fibers (DuPont's Commercial productnamed Nomex®) was knitted into a cylindrical fabric of sheeting (plainstitch fabric). The knitted fabric was heated by a hot air drier at 200°C. for 0.5 minutes. Next, this was cooled in air, and then unknittedfrom its last end. Thus unknitted, this gave crimped yarn. The tensilestrength and the lightness of the crimped yarn were measured.Concretely, the yarn was set in a constant-speed tensile tester with itsfree length between the grips being 200 mm, and tested for its tensilestrength, for which the tensile speed was 200 m/min. To measure thelightness of the yarn, used was a Suga Tester's SM color computer.

EXAMPLES 29, 30, AND COMPARATIVE EXAMPLES 7, 8

Crimped yarn was produced in the same manner as in Example 28, exceptthat the knitted fabric was heated at different temperatures as in Table6. In Examples 29 and 30, the temperature for the heat treatment fellwithin the preferred range in the invention; but in Comparative Examples7 and 8, the temperature was higher than the preferred range in theinvention.

The test results are shown in Table 6. The relationship between thetemperature in dry heat treatment and the tensile strength of the yarnis shown in FIG. 4; and the relationship between the temperature in dryheat treatment and the lightness of the yarn is in FIG. 5. As is obviousfrom FIG. 4, the tensile strength of the yarn lowered at 350 to 400° C.Also as in FIG. 5, the lightness of the yarn lowered at 350 to 400° C.,and the meta-aramid fibers that had been originally white changed intodark brown.

TABLE 6 Result in Crimped Yarn Test Condition for Heat Result in TensileTest Data in Elongation Stretch Treatment Tenacity ElongationColorimetry Percentage Modulus of Temperature Time Tenacity TenacityRetention at break Lightness in stretch Elasticity (° C.) (min) (N)(N/tex) (%) (%) (L) (%) (%) non-proce  20 — 9.05 0.41 100 17.1 74.5 5.592.5 ssed Example 28 250 0.5 — 0.41 100 — 74.5 23.7 91.1 Example 29 3000.5 9.07 0.41 100.2 17.1 71.1 50 74.8 Example 30 350 0.5 8.71 0.40 96.214.7 63   46.2 91.5 Comp. Ex. 7 400 0.5 6.36 0.29 70.3 11 58   52.5 88.3Comp. Ex. 8 450 0.5 2.22 0.10 24.5 9.0 55   — —

INDUSTRIAL APPLICABILITY

The heat-resistant crimped yarn of the invention has excellentproperties of heat resistance and flame retardancy intrinsic toheat-resistant high-functional fibers, and has a good elongationpercentage in stretch, a good stretch modulus of elasticity and a goodappearance, which conventional filament yarn and spun yarn could nothave. While produced through heat treatment, the yarn of the inventionis not substantially deteriorated. For example, the tenacity of the yarndoes not lower, the color thereof does not change, and the yarn does notfluff and cut.

Therefore, fibrous products of the heat-resistant crimped yarn of theinvention are resistant to heat and flames and are elastic. For example,gloves, working clothes and others made of the yarn well fit wearers,especially their hands. Wearing them, therefore, wearers can do theirwork and exercises with no difficulty, and feel good.

In addition, the heat-resistant crimped yarn of the invention fluffslittle and release little dust. Therefore, fibrous products, especiallyworking clothes and gloves made of the yarn are favorable to workers whowork in clean rooms for fabricating precision machines, airplanes andinformation systems, as well as to painters who paint aluminumconstruction materials, parts of electric and electronic appliances forhousehold use, automobile parts, etc.

The method for producing the heat-resistant crimped yarn of theinvention is characterized by heat-setting twisted filaments throughtreatment with high-temperature high-pressure steam or through dry heattreatment. For the high-temperature high-pressure steam treatment in themethod, usable is any ordinary autoclave or the like, in which thetwisted filaments to be heat-set may be kept at a predeterminedtemperature for a short period of time. The dry heat treatment in themethod may be affected generally under atmospheric pressure, and it maybe affected in a continuous production line. Therefore, the advantagesof the production method are that any ordinary equipment is enough forthe method, the process control is easy, the production costs arereduced, and the productivity is high. Since the heat-setting treatmentin the method is effected at temperature lower than the decompositionpoint of heat-resistant high-functional fibers, the yarn is prevented asmuch as possible from being deteriorated under heat.

What is claimed is:
 1. A method for producing a heat-resistant crimped yarn, which comprises: twisting heat-resistant high-functional fiber filaments to form a yarn, heat-setting the yarn through treatment with a high-temperature high-pressure steam or a high-temperature high-pressure water at a temperature between 130 and 250° C., and thereafter untwisting the yarn, to obtain the heat-resistant crimped yarn, wherein the heat-resistant high-functional fiber filaments are twisted to a twist parameter, K, represented by the following formula, of from 5,000 to 11,000, and are heat-set through treatment with the high-temperature high-pressure steam or the high-temperature high-pressure water at a temperature between 130 and 250° C.: K=t×D ^(1/2) wherein t indicates the count of twists (/m) of the filaments; and D indicates the fineness (tex) thereof.
 2. The method for producing the heat-resistant crimped yarn as claimed in claim 1, wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers.
 3. The method for producing the heat-resistant crimped yarn as claimed in claim 2, wherein the para-aramid fibers are polyparaphenylene-terephthalamide fibers.
 4. The method for producing the heat-resistant crimped yarn as claimed in claim 1, wherein the resultant heat-resistant crimped yarn has an elongation percentage in stretch of at least 6% and a stretch modulus of elasticity of at least 40%.
 5. A method for producing a heat-resistant crimped yarn, which comprises: twisting heat-resistant high-functional fiber filaments to form a yarn, heat-setting the yarn through a dry heat treatment at a temperature between 140 and 390° C., and thereafter untwisting the yarn to obtain the heat-resistant crimped yarn, wherein the heat-resistant high-functional fiber filaments are twisted to a twist parameter, K, represented by the following formula, of from 5,000 to 11,000, then the yarn is heat-set through the dry heat treatment at a temperature between 140 and 390° C., and thereafter the yarn is untwisted: K=t×D ^(1/2) wherein t indicates the count of twists (/m) of the filaments; and D indicates the fineness (tex) thereof.
 6. The method for producing the heat-resistant crimped yarn as claimed in claim 5, wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers.
 7. The method for producing the heat-resistant crimped yarn as claimed in claim 6, wherein the para-aramid fibers are polyparaphenylene-terephthalamide fibers.
 8. The method for producing the heat-resistant crimped yarn as claimed in claim 5, wherein the resultant heat-resistant crimped yarn has an elongation percentage in stretch of at least 6% and a stretch modulus of elasticity of at least 40%.
 9. A method for producing a heat-resistant crimped yarn, which comprises: knitting heat-resistant high-functional fiber filaments into a knitted fabric, then heat-setting the knitted fabric through a dry heat treatment at a temperature between 140 and 390° C. or through a treatment with a high-temperature high-pressure steam or a high-temperature high-pressure water at a temperature between 130 and 250° C., and thereafter unknitting the fabric, to obtain the heat-resistant crimped yarn, wherein the knitted fabric of heat-resistant high-functional fiber filaments is heat-set through treatment with the high-temperature high-pressure steam or the high-temperature high-pressure water at a temperature between 130 and 250° C. for a period of time between 2 and 100 minutes, and then the knitted fabric is unknitted.
 10. The method for producing the heat-resistant crimped yarn as claimed in claim 9, wherein the resultant heat-resistant crimped yarn has an elongation percentage in stretch of at least 6.5%.
 11. The method for producing the heat-resistant crimped yarn as claimed in claim 9, wherein the heat-resistant high-functional fibers are selected from the group consisting of para-aramid fibers, meta-aramid fibers, holaromatic polyester fibers and polyparaphenylene-benzobisoxazole fibers. 